A valve train of the pre-cited type is disclosed in U.S. Pat. No. 6,196,175 B1. The tappet of this valve train is configured as a switchable roller tappet and is installed in a relatively strongly restricted mounting space, so that only an inadequate quantity of hydraulic medium can be contained in its pressure piston. However, in various situations such as upon re-firing of the internal combustion engine after a longer standstill, “taxi operation” etc., this hydraulic medium proves to be insufficient for a proper lash adjusting operation of the lash adjuster. Therefore, a relatively high risk of a re-aspiration of air into the high pressure chamber of the lash adjuster exists with all the drawbacks, like rattling noises, wear etc., known in the technical field.
Moreover, it is usual in OHV trains comprising a roller tappet and a tappet pushrod to lubricate further components like rocker arms, cam-contacting surfaces etc. that are situated at a high geodetic level, through a hollow tappet pushrod. This is also disclosed in the pre-cited U.S. Pat. No. 6,196,175, while U.S. Pat. No. 3,908,615 likewise discloses a hollow tappet pushrod. Further, U.S. Pat. No. 5,351,662 shows a tappet configured as a roller tappet in which it can be seen that, for design reasons, the hydraulic lash adjuster can contain only a very small quantity of hydraulic medium.